Lederman, Steinberger, and Schwartz et al. report the discovery of a second neutrino flavor
American physicists Leon Lederman, Melvin Schwartz, and Jack Steinberger joined forces to search for another type of neutrino at Brookhaven National Laboratory on Long Island, New York. At the time, only the electron neutrino was known.
Their experiment shot a powerful beam of protons at a beryllium target, producing large numbers of pions that would then decay into muons and neutrinos. Only the latter particles could pass through the wall into a neon-filled detector called a spark chamber. There, neutrinos that interacted with protons in the aluminum plates produced muons that could be detected and photographed by their spark trails—proving the existence of muon-neutrinos.